The present invention relates to a robot controller having a display unit disposed apart from a body of a robot controller.
To display image data on a display unit, it is necessary to connect a graphic control circuit (Video Graphics Array, VGA) adapted to the interface of the display unit to the display unit. To transmit image data from the VGA controller to the display unit, there are a method using a digital VGA controller to transmit data in the form of a digital signal and a method using an analog VGA controller to transmit data in the form of an analog signal.
When the digital VGA controller is employed, each of R (red), G (green) and B (blue) color signals is composed of four bits, as shown in FIG. 3. A horizontal synchronizing signal (HSYNC), a vertical synchronizing signal (VSYNC) and a data enable signal (DE) are required as synchronizing signals. Thus, fifteen signal lines are required.
When the analog VGA controller is employed, R, G, B color signals are transmitted in the form of analog signals from the VGA controller to the display unit through three signal lines. Then, the analog signal undergoes A/D conversion on the display unit side for adaption to the interface of the display unit. One signal line is required for each of the horizontal synchronizing signal (HSYNC) and the vertical synchronizing signal (VSYNC). Moreover, a data enable signal (DE) must sometimes be transmitted, requiring therefore five or six signal lines in total.
Industrial robots use a variety of data which must be displayed on the display unit. When image data transmitted from a VGA controller of a card personal computer or the like mounted on a robot control unit is displayed on the display unit, 15 signal lines are required for the digital VGA controller and 5 (or 6) signal lines are required for the analog VGA controller as described above.
A digital VGA controller transmits signals accurately because the signals transmitted are digital. However, in the case where a display unit is disposed separated from the body of a robot controller, mere extension of a signal line would hinder normal transmission of signals because signals from a digital VGA are of TTL (Transistor-Transistor-Logic) level so that they tend to lower in level in the signal line. Therefore, the signal has to be transmitted in the form of a differential output (that is, data is transmitted based on the difference between each signal and an inversion signal of the signal). In order to do so, signal lines for transmitting the inversion signals are required, thus causing the number of signal lines to be doubled. For example, in the case of the system shown in FIG. 3, the number of signal lines will be impractical number of lines (15xc3x9720).
On the other hand, in the case of the analog VGA controller, the number of the signal lines can be reduced, but the A/D converter is required as described above, and this requires the use of coaxial cable having a larger diameter and thus being less flexible in handling when the display unit such as a teaching pendant has to be held by a hand for operation. Since signal to be transmitted is analog, the signal level is lowered and thus the number of colors which can be displayed is limited, and further, differences in delays are produced among each color so that deviation from synchronization takes place.
An object of the present invention is to provide a robot controller capable of accurately transmitting image data and employing a flexible cable even if a display unit is disposed apart from a body of the robot controller.
To achieve the above-mentioned object, in a robot controller according to one aspect of the present invention, a display unit is separated from the body of the robot controller, the body of the robot controller and the display unit are connected to each other through a twisted pair line or a coaxial cable, and image data from a graphic control circuit provided on the body of the robot controller is converted into serial data and transmitted to the display unit.
Further, in a robot controller according to the other aspect of the present invention, a display unit is separated from the body of the robot controller, a driver provided on the body of the robot controller and a receiver provided on the display unit are connected to each other through a twisted pair line or a coaxial cable, the driver and the receiver are provided with a phase-locked loop circuit for phasing the both with each other, and image data supplied from a graphic control circuit provided on the body of the robot controller is divided into two sections so that high speed serial communication can be performed at double speed.
Further, in a robot controller according to still other aspect of the present invention, wherein a display unit is separated from the body of the robot controller, and the body of the robot controller and the display unit are connected to each other through a twisted pair line or a coaxial cable. And the body of the robot controller comprises: a latch circuit for latching image data transmitted from the graphic control circuit by a quantity corresponding to several pixels; a RAM for sequentially storing image data corresponding to several pixels latched by the latch circuit; a driver for sequentially transmitting, to the twisted pair line or the coaxial cable, image data corresponding to several pixels stored in the RAM; and a control circuit for controlling the latching of image data to be performed by the latch circuit, writing and reading of image data to and from the RAM and transmission of image data corresponding to several pixels from the RAM to the twisted pair line or the coaxial cable by the driver. And the display unit comprises: a receiver connected to the twisted pair line or the coaxial cable; a RAM for sequentially storing image data for several pixels received by the receiver; a latch circuit for latching image data for several pixels read from the RAM and transmitting image data for one pixel at a time to a display unit; a display unit itself; and a control circuit for controlling writing and reading of image data for several pixels supplied from the receiver on and from the RAM, latching of image data for several pixels to be performed by the latch circuit, and separating and transmitting of image data for one pixel from image data for the plurality of pixels latched by the latch circuit so that high speed serial communication can be performed.
The present invention is designed so that image data is transmitted to the display unit by high speed serial communication, and, moreover, the transmission line is of the twisted pair line or the coaxial cable having small number of cores. Therefore, an accurate image can be obtained and the cable has a sufficient flexibility, so that the operability of a teaching pendant or the like, on which the display unit is mounted, can be improved.